The present invention relates to an apparatus for the precision treatment of a material such as high-purity silicon semiconductor wafers in which a monitoring means for detecting the end point of the plasma reaction is provided.
In the recent development of the semiconductor technology, a dry method of plasma etching is obtaining more and more wide applications in place of the conventional wet etching method with an etching solution giving a possibility of very fine working in the manufacture of ICs, LSIs, ultra-LSIs and the like. In spite of the very apparent advantages of the plasma etching method over the wet method, it is only recently that the method has come into current because of the difficulty in detecting the end point of the etching by the plasma reaction as a major problem.
Attempts have been made for monitoring the progress of the plasma reaction by spectrophotometrically recording the light emitted from the plasma through a window in the plasma reaction chamber with an expensive equipment composed of a grating spectrometer and a photomultiplier recording system (see W. R. Harshbarger et al., Kodak Microelectronics Seminar, October, 1976).